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Abstract:

There is provided an inductive coupler for coupling a signal to a power
line. The inductive coupler includes (a) a magnetic core having an
aperture through which the power line is routed, (b) a winding wound
around a portion of the magnetic core, where the signal is coupled
between the winding and the power line via the magnetic core, and (c) an
electrically conductive member on an exterior of the inductive coupler
that provides a path to electrical ground for a flashover current.

Claims:

1. An inductive coupler for coupling a signal to a conductor, comprisinga
magnetic core having an aperture through which said conductor is routed
when said inductive coupler is installed on said conductor;a winding
wound around a portion of said magnetic core, wherein said signal is
coupled between said winding and said conductor via said magnetic core;
andan electrically conductive member on an exterior of said inductive
coupler that provides a path to electrical ground for a flashover
current.

2. The inductive coupler of claim 1, further comprising a connection that
connects said member to said electrical ground.

3. The inductive coupler of claim 1, wherein said member is at electrical
ground potential.

4. The inductive coupler of claim 1, wherein said member is a fitting on a
surface of said inductive coupler.

5. The inductive coupler of claim 1, wherein said member is an exposed
surface on a conductor connected to said inductive coupler.

6. An inductive coupler for coupling a signal to a conductor, comprisinga
magnetic core having an aperture through which said conductor is routed
when said inductive coupler is installed on said conductor;a winding
wound around a portion of said magnetic core, wherein said signal is
coupled between said winding and said conductor via said magnetic core;
anda member on a surface of said inductive coupler, wherein said member
is electrically conductive, at electrical ground potential, and provides
a path to electrical ground for a flashover current.

7. An inductive coupler for coupling a signal to a power line, comprisinga
magnetic core having an aperture through which said power line is routed
when said inductive coupler is installed on said power line;a winding
wound around a portion of said magnetic core, wherein said signal is
coupled between said winding and said power line via said magnetic core;
anda conductor on an exterior of said inductive coupler, wherein said
conductor has an exposed surface, is at electrical ground potential, and
provides a path to electrical ground for a flashover current.

8. The inductive coupler of claim 1, wherein said flashover current is due
to a flashover from said conductor.

9. A method comprising:situating an inductive coupler on a power line,
wherein said inductive coupler has an electrically conductive member on
an exterior surface thereof; andconnecting said electrically conductive
member to an electrical ground.

10. The method of claim 9, wherein said connecting provides a path, via
said electrically conductive member to said electrical ground, for a
flashover current.

11. The method of claim 10, wherein said flashover current is due to a
flashover from said power line.

12. The method of claim 11, wherein said inductive coupler comprises:a
magnetic core having an aperture through which said power line is routed
when said inductive coupler is installed on said power line; anda winding
wound around a portion of said magnetic core.

13. The method of claim 12, wherein said magnetic core couples a data
signal between said winding and said power line.

14. The method of claim 13, wherein said data signal has a frequency of
greater than or equal to about 1 megahertz.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to power line communications, and more
particularly, to a configuration of a data coupler for power line
communications.

[0003]2. Description of the Related Art

[0004]Power line communications (PLC), also known as broadband over power
line (BPL), is a technology that encompasses transmission of data at high
frequencies through existing electric power lines, i.e., conductors used
for carrying a power current. A data coupler for power line
communications couples a data signal between a power line and a
communication device such as a modem.

[0005]An example of such a data coupler is an inductive coupler that
includes a set of cores, and a winding wound around a portion of the
cores. The inductive coupler operates as a transformer, where the cores
are situated on a power line such that the power line serves as a primary
winding of the transformer, and the winding of the inductive coupler is a
secondary winding of the transformer.

[0006]The cores are typically constructed with magnetic materials, such as
ferrites, powdered metal, or nano-crystalline material. The cores are
electrified by contact with the power line and require insulation from
the secondary winding. Typically, insulation is provided between the
cores and secondary winding by embedding both the cores and the secondary
winding in electrically insulating material, such as epoxy.

[0007]An inductive coupler is required to meet safety requirements to
avoid injury to personnel performing installation, maintenance and
removal of communications equipment. At times a phenomenon may occur
where the voltage exceeds the utility line voltage class rating. At this
elevated voltage, air, water or any other foreign gas, liquid or solid
particle found in an outdoor environment can act as a conductive path
allowing for a disruptive discharge over the surface of a solid
insulation. The industry terms this occurrence, flashover (reference:
IEEE 4-1995 Standard, Techniques for High Voltage Testing). A flashover
to an insulated conductor of an inductive coupler may puncture the
insulation of the conductor, and/or damage the conductor itself. The
puncture or damage is considered a failure of the inductive coupler, and
should be avoided.

SUMMARY OF THE INVENTION

[0008]There is provided an inductive coupler for coupling a signal to a
power line. The inductive coupler includes (a) a magnetic core having an
aperture through which the power line is routed, (b) a winding wound
around a portion of the magnetic core, wherein the signal is coupled
between the winding and the power line via the magnetic core, and (c) an
electrically conductive member on an exterior of the inductive coupler
that provides a path to electrical ground for a flashover current.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a three dimensional view of an inductive coupler installed
on a power line showing an intended location for flashover to discharge
to electrical ground.

[0011]FIG. 2A is a schematic of a portion of the inductive coupler of FIG.
1.

[0012]FIG. 3 is a three dimensional view of an inductive coupler installed
on a power line having an intended path for flashover to the coupler's
grounded secondary winding.

DESCRIPTION OF THE INVENTION

[0013]In a PLC system, power current is typically transmitted through a
power line at a frequency in the range of 50-60 hertz (Hz). In a low
voltage line, power current is transmitted with a voltage between about
90 to 600 volts, and in a medium voltage line, power current is
transmitted with a voltage between about 2,400 volts to 35,000 volts. The
frequency of the data signals is greater than or equal to about 1
megahertz (MHz), and the voltage of the data signal ranges from a
fraction of a volt to a few tens of volts.

[0014]FIG. 1 is a three dimensional view of an inductive coupler 100 on a
conductor, i.e., a power line 120. Inductive coupler 100 includes a
magnetic core (not shown), and a winding (see FIG. 2, reference 205),
wound around a portion of the magnetic core. The magnetic core is
generally, cylindrical-shaped, having an aperture the length of the
cylinder, and power line 120 is routed through the aperture. Inductive
coupler 100 operates as a transformer, where power line 120 serves as a
primary winding of the transformer, and winding 205 is a secondary
winding of the transformer.

[0015]As a voltage on power line 120 increases in magnitude with respect
to electrical ground, the voltage may reach a magnitude at which a
flashover will occur between power line 120 and a surface that is at
ground potential. If a plurality of surfaces exist at similar distances
from power line 120, and if some of these surfaces are conductive and
others of these surfaces are non-conductive, the flashover is more likely
to occur between power line 120 and one of the conductive surfaces.

[0016]A ground cable 110 and a coaxial cable 115 protrude out of a side of
inductive coupler 100. An exposed end of ground cable 110 is fastened to
a ground rod (not shown). Coaxial cable 115 is for connection with a
modem or other communications equipment (not shown).

[0018]FIG. 2 is another illustration of inductive coupler 100, and shows a
configuration of several internal components. Inductive coupler 100
includes a winding 205, as mentioned above. Winding 205 is a length of
conductive material, e.g., a wire, having two ends, i.e., a winding side
205A and a winding side 205B.

[0019]FIG. 2A is a schematic showing electrical connections between
several of the components of inductive coupler 100.

[0021]A ground cable jacket 245 provides insulation between conductor 250
and cable housing fitting 105A, and as mentioned above, coaxial cable
jacket 240 provides insulation between cable housing fitting 105B and
sheath 220. However, an electrical connection 200 connects cable housing
fittings 105A and 105B to winding side 205A, and an electrical connection
210 connects winding side 205A to an exposed conductor, i.e., a conductor
250, of ground cable 110. Thus, cable housing fittings 105A and 105B are
electrically grounded. If a flashover were to discharge through ground
cable jacket 245 or coaxial cable jacket 240, the insulation could be
damaged by the flashover current. However, since cable housing fittings
105A and 105B are conductive and electrically grounded, cable housing
fittings 105A and 105B would attract the flashover current, and provide a
path to ground through electrical connection 200, winding side 205A,
electrical connection 210 and ground cable 110.

[0022]As mentioned above, FIG. 2A is a schematic. As such, FIG. 2A is
intended to represent electrical connections, and not necessarily a
physical embodiment of the connections. For example, electrical
connection 200 could be in a form of a metal plate, and be directly
connected to ground cable 110 rather than to winding side 205A. In any
case, each of cable housing fittings 105A and 105B, electrical connection
200, winding side 205A, electrical connection 210 and ground cable 110
are at electrical ground potential, and are of an adequate size to
accommodate any current that they are expected to handle.

[0023]FIG. 3 shows an inductive coupler 300 where winding 205 is connected
to cables 310 such that there are exposed surfaces 305 on a conductor
connected to inductive coupler 300. Surfaces 305, as shown in FIG. 3, are
surfaces of electrically conductive connectors situated at points where
winding 205 is connected to cables 310. Provided that cables 310 lead to
electrical equipment (not shown) that connects winding 205 to electrical
ground, exposed electrically conductive surfaces of cable 310, and/or
exposed surface 305, as well as winding 205's exposure below coupler
insulation 315, can individually or collectively function as a potential
path to electrical ground for flashover current.

[0024]The techniques described herein are exemplary, and should not be
construed as implying any particular limitation on the present invention.
It should be understood that various alternatives, combinations and
modifications could be devised by those skilled in the art. The present
invention is intended to embrace all such alternatives, modifications and
variances that fall within the scope of the appended claims.